High efficiency illumination sources, such as those used in projector systems, industrial lighting fixtures, stadium lighting, and so forth, may make use of a metal halide vapor that is electrically excited in order to produce light. To activate the illumination source, a ballast or other device is used to deliver a controlled current and voltage waveform to the illumination source. The waveforms typically begin with an initial high-voltage segment that activates the illumination source while the source is preferably in a “cold” state. Subsequently, the voltage delivered to the illumination source is reduced as the illumination source assumes steady-state operation.
When the input power to a high efficiency metal vapor illumination source is removed, sufficient time should be allowed before restarting the illumination source so that the metal halide vapor can be allowed to condense. If the illumination source is not allowed to sufficiently cool before being reactivated, the presence of a large voltage at the input to the source can cause a large current to flow through the metal halide vapor. These high-current and high-voltage events can damage the electrodes within the illumination source, thus causing the lamp to fail or to significantly reduce the operating life of the illumination source.